1. Field of the Invention
This invention relates to a method for connecting semiconductor material, more particularly a connecting method applied when a wireless bonding method, in particular a flip tip bonding method or a tape carrier bonding method are applied for bonding semiconductor tips to a substrate, connection material to be used in the connection method and semiconductor devices manufactured by the above-mentioned connection method.
2. Description of the Prior Art
As the conventional system for forming a bump electrode by using a wire bonding machine, there are Jap. Pat. Laid-Open Nos. 61-43438 and 61-219159. In the prior art, after the bump electrode is bonded, the desired position of the wire is cut by an electrical discharging with an electric torch in order to make a specified size of the wire remained in the ball.
The above-mentioned prior art showed a problem that a processing step was complicated and an efficiency of the work was decreased.
As other connecting methods, as disclosed in Jap. Pat. Laid-Open No. 59-208751, the wire is clamped with a clamper after bonding operation and cut while being pulled up, i.e. a connecting method requiring no special cutting method is disclosed. However, as described in the above gazette, although a mere clamping and pulling up the wire with a clamper enables the wire to be cut, but it is impossible to keep always a size of the wire remained in the ball constant, to perform s continuous stable bonding operation and to provide a semiconductor device having a high reliability.
At present, as a bump electrode material, PbSn of 5 wt %, PbSn of 40 wt % or the like is used. However, it has been found that a connection of alloy wire made by drawing the alloy manufactured by a normal casting method through a die under an operation of the wire bonder shows a frequent cutting of the wire not at the root part of the ball but at a midway part of the wire, a substantial disturbance in its length and so the wire is not suitable as a bump electrode.
Cutting of the alloy wire at the wire part is caused by the fact that a tensile strength of the root part of the ball is not sufficiently low as compared with a tensile strength of the wire part.
Due to this reason, the conventional method described in Jap. Pat. Laid-Open No. 59-208751 can not always keep the size of wire remained in the ball constant.